From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CFDDC48BE3 for ; Fri, 21 Jun 2019 01:03:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 164662085A for ; Fri, 21 Jun 2019 01:03:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="YT9pP8mm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726192AbfFUBDU (ORCPT ); Thu, 20 Jun 2019 21:03:20 -0400 Received: from mail-pf1-f196.google.com ([209.85.210.196]:34085 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725951AbfFUBDU (ORCPT ); Thu, 20 Jun 2019 21:03:20 -0400 Received: by mail-pf1-f196.google.com with SMTP id c85so2656219pfc.1 for ; Thu, 20 Jun 2019 18:03:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=message-id:mime-version:content-transfer-encoding:in-reply-to :references:to:from:subject:cc:user-agent:date; bh=/QNfQWig2oeC5POufHOkxnAuAVkUYpsqHyVQpvyXPFM=; b=YT9pP8mmnoLSnibB3gevIC8O4iva3l7WbYe+TvJLiuO8Sl8rGyxguOWdu9Xkz3aMFK 0JcQpSOWMOO4Ipb2MWZdlgVt1gqKnEVbbl/k08kEf7rdSzKoGFDVsTEq54pldf9AvuOi AEJ/VAYyprATMD4PR72B+IkMkBKhPYLYh7Sug= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:mime-version :content-transfer-encoding:in-reply-to:references:to:from:subject:cc :user-agent:date; bh=/QNfQWig2oeC5POufHOkxnAuAVkUYpsqHyVQpvyXPFM=; b=bQFWkMUP3D7sQeg+2h/eCdgQ8AWIOKbRCGIbM3WG7JE8ae4VxekkyuE7SAi048SRZi yzvcrx7HU/zO3NROqaYq8vm7QatOcjbXZilW629jZoKI/2nuDZg3k+958enmHTKfphMT ivtZhrYizEPcZEG60BPnKITSqcRvgKA1wUQPzBdkF8457HHG+LpItaL9DAezo9L2MeJG ghh9d3Lw2yCMelQ7KbXyIdP+vUc4/aHH58O3MDBm/qVnpOlJviWAQcgx58EtF/k/xnSi P1RLk+vfgR6iOdvHyF6qNXYkImQ07GViZ89whxZDPUE6kO+DDdBKIcc5vEvjW5iJxlgS Xdzg== X-Gm-Message-State: APjAAAUNzqdNcVUVZ84g4c6VkpoaE7JfoiH8e5aYLR7YCBRBMO6Yaea9 d9GOOo1k6hSebHGZ2H8QUEdI3Q== X-Google-Smtp-Source: APXvYqw5MjR8b5QF1inGOhF3D0ddQ3KFCau26pbHfnEVTRxI5c2/WPbsRNarL55GkCl3Ecm1fJ+H/A== X-Received: by 2002:a63:3c14:: with SMTP id j20mr3859916pga.169.1561078999454; Thu, 20 Jun 2019 18:03:19 -0700 (PDT) Received: from chromium.org ([2620:15c:202:1:fa53:7765:582b:82b9]) by smtp.gmail.com with ESMTPSA id y185sm634195pfy.110.2019.06.20.18.03.18 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 20 Jun 2019 18:03:18 -0700 (PDT) Message-ID: <5d0c2cd6.1c69fb81.e66af.32bf@mx.google.com> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable In-Reply-To: <20190617225134.GA30762@ziepe.ca> References: <20190613180931.65445-1-swboyd@chromium.org> <20190613180931.65445-2-swboyd@chromium.org> <20190613232613.GH22901@ziepe.ca> <5d03e394.1c69fb81.f028c.bffb@mx.google.com> <20190617225134.GA30762@ziepe.ca> To: Jason Gunthorpe From: Stephen Boyd Subject: Re: [PATCH 1/8] tpm: block messages while suspended Cc: Peter Huewe , Jarkko Sakkinen , Andrey Pronin , linux-kernel@vger.kernel.org, Arnd Bergmann , Greg Kroah-Hartman , linux-integrity@vger.kernel.org, devicetree@vger.kernel.org, Duncan Laurie , Guenter Roeck , Matt Mackall , Herbert Xu , User-Agent: alot/0.8.1 Date: Thu, 20 Jun 2019 18:03:17 -0700 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Jason Gunthorpe (2019-06-17 15:51:34) > On Fri, Jun 14, 2019 at 11:12:36AM -0700, Stephen Boyd wrote: > > Quoting Jason Gunthorpe (2019-06-13 16:26:13) > > > On Thu, Jun 13, 2019 at 11:09:24AM -0700, Stephen Boyd wrote: > > > > From: Andrey Pronin > > > >=20 > > > > Other drivers or userspace may initiate sending a message to the tpm > > > > while the device itself and the controller of the bus it is on are > > > > suspended. That may break the bus driver logic. > > > > Block sending messages while the device is suspended. > > > >=20 > > > > Signed-off-by: Andrey Pronin > > > > Signed-off-by: Stephen Boyd > > > >=20 > > > > I don't think this was ever posted before. > > >=20 > > > Use a real lock. > > >=20 > >=20 > > To make sure the bit is tested under a lock so that suspend/resume can't > > update the bit in parallel? >=20 > No, just use a real lock, don't make locks out of test bit/set bit >=20 Ok. I looked back on the history of this change in our kernel (seems it wasn't attempted upstream for some time) and it looks like the problem may have been that the khwrng kthread (i.e. hwrng_fill()) isn't frozen across suspend/resume. This kthread runs concurrently with devices being resumed, the cr50 hardware is still suspended, and then a tpm command is sent and it hangs the I2C bus because the device hasn't been properly resumed yet. I suspect a better approach than trying to hold of all TPM commands across suspend/resume would be to fix the caller here to not even try to read the hwrng during this time. It's a general problem for other hwrngs that have some suspend/resume hooks too. This kthread is going to be running while suspend/resume is going on if the random entropy gets too low, and that probably shouldn't be the case. What do you think of the attached patch? I haven't tested it, but it would make sure that the kthread is frozen so that the hardware can be resumed before the kthread is thawed and tries to go touch the hardware. ----8<----- diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 95be7228f327..3b88af3149a7 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -421,7 +422,9 @@ static int hwrng_fillfn(void *unused) { long rc; =20 - while (!kthread_should_stop()) { + set_freezable(); + + while (!kthread_freezable_should_stop(NULL)) { struct hwrng *rng; =20 rng =3D get_current_rng();